Compressor Equipment

Documentation for compression equipment in NeqSim process simulation.

Table of Contents

📖 Detailed Curve Documentation: For comprehensive information on compressor curves, including multi-speed vs single-speed handling, surge curves, and stone wall curves, see Compressor Curves and Performance Maps.

Overview

Location: neqsim.process.equipment.compressor

Classes:

Basic Usage

import neqsim.process.equipment.compressor.Compressor;

Compressor compressor = new Compressor("K-100", inletStream);
compressor.setOutletPressure(80.0, "bara");
compressor.setIsentropicEfficiency(0.75);
compressor.run();

// Results
double power = compressor.getPower("kW");
double outletT = compressor.getOutletStream().getTemperature("C");
double polytropicHead = compressor.getPolytropicHead("kJ/kg");

System.out.println("Power: " + power + " kW");
System.out.println("Outlet temperature: " + outletT + " °C");

Calculation Methods

Isentropic Compression

compressor.setIsentropicEfficiency(0.75);  // 75%
compressor.setUsePolytropicCalc(false);
compressor.run();

double isentropicHead = compressor.getIsentropicHead("kJ/kg");
double isentropicPower = compressor.getPower("kW");

Polytropic Compression

More accurate for real gas behavior.

compressor.setPolytropicEfficiency(0.80);  // 80%
compressor.setUsePolytropicCalc(true);
compressor.run();

double polytropicHead = compressor.getPolytropicHead("kJ/kg");
double polytropicExponent = compressor.getPolytropicExponent();

Power Specified

compressor.setPower(5000.0, "kW");  // Specify power
compressor.setIsentropicEfficiency(0.75);
compressor.run();

double outletP = compressor.getOutletStream().getPressure("bara");

Efficiency Relationships

Isentropic Efficiency

\[\eta_{is} = \frac{H_{is}}{H_{actual}} = \frac{T_{2s} - T_1}{T_2 - T_1}\]

Polytropic Efficiency

\[\eta_p = \frac{n-1}{n} \cdot \frac{k}{k-1}\]

Where:

Performance Curves

NeqSim supports detailed compressor performance maps with multiple speed curves. For comprehensive documentation, see Compressor Curves and Performance Maps.

Setting Compressor Map

// Define speed curves
double[] speeds = {8000, 9000, 10000, 11000};  // RPM

// For each speed: arrays of flow, head, efficiency
double[][] flows = { {flow1_curve1, flow2_curve1}, {flow1_curve2, flow2_curve2}, ... };
double[][] heads = { {head1_curve1, head2_curve1}, {head1_curve2, head2_curve2}, ... };
double[][] efficiencies = { {eff1_curve1, eff2_curve1}, {eff1_curve2, eff2_curve2}, ... };

CompressorChartInterface chart = compressor.getCompressorChart();
chart.setCurves(chartConditions, speeds, flows, heads, flows, efficiencies);
chart.setHeadUnit("kJ/kg");
compressor.setSpeed(10000);  // Operating speed

Operating Point

compressor.setSpeed(10000);  // RPM
compressor.run();

double actualFlow = compressor.getActualFlow("m3/hr");
double head = compressor.getPolytropicHead("kJ/kg");
double efficiency = compressor.getPolytropicEfficiency();

Surge and Stone Wall

Multi-Speed vs Single-Speed Compressors

Compressor Type Surge/Stone Wall Setting Method
Multi-speed (≥2 speeds) Curves (interpolated) Multiple flow/head points
Single-speed (1 speed) Single points (constant) Single flow/head point

Checking Operating Limits

// Distance to surge (positive = above surge, safe)
double distanceToSurge = compressor.getDistanceToSurge();

// Distance to stone wall (positive = below choke, safe)
double distanceToStoneWall = compressor.getDistanceToStoneWall();

// Check if in surge
boolean isSurge = compressor.getCompressorChart().getSurgeCurve().isSurge(head, flow);

// Get surge flow rate
double surgeFlow = compressor.getSurgeFlowRate();

Single-Speed Compressor Example

// For single-speed compressors, surge is a single point
double[] surgeFlow = {5607.45};  // Single value
double[] surgeHead = {150.0};   // Single value
compressor.getCompressorChart().getSurgeCurve().setCurve(chartConditions, surgeFlow, surgeHead);

// Stone wall is also a single point
double[] stoneWallFlow = {9758.49};
double[] stoneWallHead = {112.65};
compressor.getCompressorChart().getStoneWallCurve().setCurve(chartConditions, stoneWallFlow, stoneWallHead);

📖 See Also: Compressor Curves and Performance Maps for detailed documentation on curve setup, interpolation methods, and Python examples.

Compressor Staging

Multi-Stage with Intercooling

ProcessSystem process = new ProcessSystem();

// Stage 1: 20 -> 50 bar
Compressor stage1 = new Compressor("K-100A", inletStream);
stage1.setOutletPressure(50.0, "bara");
stage1.setPolytropicEfficiency(0.78);
process.add(stage1);

// Intercooler
Cooler intercooler = new Cooler("E-100", stage1.getOutletStream());
intercooler.setOutTemperature(40.0, "C");
process.add(intercooler);

// Stage 2: 50 -> 120 bar
Compressor stage2 = new Compressor("K-100B", intercooler.getOutletStream());
stage2.setOutletPressure(120.0, "bara");
stage2.setPolytropicEfficiency(0.78);
process.add(stage2);

// Aftercooler
Cooler aftercooler = new Cooler("E-101", stage2.getOutletStream());
aftercooler.setOutTemperature(40.0, "C");
process.add(aftercooler);

process.run();

// Total power
double totalPower = stage1.getPower("kW") + stage2.getPower("kW");
System.out.println("Total compression power: " + totalPower + " kW");

Optimal Pressure Ratio

For minimum work with equal stage ratios:

\[r_{stage} = \left(\frac{P_{out}}{P_{in}}\right)^{1/n}\] 
double overallRatio = 120.0 / 20.0;  // 6:1
int numStages = 2;
double stageRatio = Math.pow(overallRatio, 1.0 / numStages);  // √6 ≈ 2.45

Antisurge Control

// Recycle valve for antisurge
Splitter recycle = new Splitter("Antisurge Recycle", stage2.getOutletStream());
recycle.setSplitFactors(new double[]{0.9, 0.1});  // 10% recycle

// Mix with inlet
Mixer mixer = new Mixer("Inlet Mixer");
mixer.addStream(inletStream);
mixer.addStream(recycle.getSplitStream(1));

Power Calculation Details

Real Gas Effects

// Account for compressibility
double Z1 = compressor.getInletStream().getZ();
double Z2 = compressor.getOutletStream().getZ();
double Zavg = (Z1 + Z2) / 2;

Mechanical Efficiency

// Include mechanical losses
compressor.setMechanicalEfficiency(0.98);
double shaftPower = compressor.getShaftPower("kW");
double gasHorsepower = compressor.getGasHorsepower("hp");

Example: Export Gas Compression

// Export gas at 100 MSm³/day
SystemInterface gas = new SystemSrkEos(288.15, 30.0);
gas.addComponent("methane", 0.92);
gas.addComponent("ethane", 0.04);
gas.addComponent("propane", 0.02);
gas.addComponent("CO2", 0.01);
gas.addComponent("nitrogen", 0.01);
gas.setMixingRule("classic");

Stream inlet = new Stream("Inlet Gas", gas);
inlet.setFlowRate(100.0, "MSm3/day");
inlet.setTemperature(30.0, "C");
inlet.setPressure(30.0, "bara");

ProcessSystem process = new ProcessSystem();
process.add(inlet);

// 3-stage compression to 200 bar
double[] stagePressures = {55, 105, 200};

Stream currentStream = inlet;
for (int i = 0; i < 3; i++) {
    Compressor comp = new Compressor("K-10" + (i+1), currentStream);
    comp.setOutletPressure(stagePressures[i], "bara");
    comp.setPolytropicEfficiency(0.78);
    comp.setUsePolytropicCalc(true);
    process.add(comp);
    
    Cooler cooler = new Cooler("E-10" + (i+1), comp.getOutletStream());
    cooler.setOutTemperature(40.0, "C");
    process.add(cooler);
    
    currentStream = cooler.getOutletStream();
}

process.run();

// Report
System.out.println("\n=== Compression Summary ===");
double totalPower = 0;
for (int i = 1; i <= 3; i++) {
    Compressor c = (Compressor) process.getUnit("K-10" + i);
    totalPower += c.getPower("MW");
    System.out.printf("Stage %d: %.2f bar -> %.2f bar, %.2f MW%n",
        i, c.getInletStream().getPressure("bara"),
        c.getOutletStream().getPressure("bara"),
        c.getPower("MW"));
}
System.out.println("Total power: " + totalPower + " MW");

Automatic Curve Generation

When manufacturer performance data is not available, NeqSim can automatically generate realistic compressor curves using predefined templates.

Quick Start

// 1. Create and run compressor to establish design point
Compressor comp = new Compressor("K-100", inletStream);
comp.setOutletPressure(100.0, "bara");
comp.setPolytropicEfficiency(0.78);
comp.setSpeed(10000);
comp.run();

// 2. Generate curves from template
CompressorChartGenerator generator = new CompressorChartGenerator(comp);
CompressorChartInterface chart = generator.generateFromTemplate("PIPELINE", 5);

// 3. Apply and use
comp.setCompressorChart(chart);
comp.run();

Available Templates

Category Templates
Basic CENTRIFUGAL_STANDARD, CENTRIFUGAL_HIGH_FLOW, CENTRIFUGAL_HIGH_HEAD
Application PIPELINE, EXPORT, INJECTION, GAS_LIFT, REFRIGERATION, BOOSTER
Type SINGLE_STAGE, MULTISTAGE_INLINE, INTEGRALLY_GEARED, OVERHUNG

Template Selection

Use Case Recommended Template
Gas transmission PIPELINE
Offshore export EXPORT
Gas injection/EOR INJECTION
Artificial lift GAS_LIFT
LNG/refrigeration REFRIGERATION
General purpose CENTRIFUGAL_STANDARD

📖 Detailed Documentation: See Compressor Curves - Automatic Generation for complete API reference, advanced corrections, and examples.

Mechanical Losses and Seal Gas

NeqSim supports modeling of compressor mechanical losses and seal gas consumption per API 617 (bearings) and API 692 (dry gas seals).

Overview

The CompressorMechanicalLosses class models:

Component Standard Description
Dry Gas Seals API 692 Primary/secondary leakage, buffer gas, separation gas
Bearings API 617 Radial and thrust bearing friction losses
Lube Oil System API 614 Oil flow requirements and cooler duty

Quick Start

// Create and run compressor
Compressor compressor = new Compressor("K-100", inletStream);
compressor.setOutletPressure(100.0, "bara");
compressor.setSpeed(10000);
compressor.run();

// Initialize mechanical losses with shaft diameter (mm)
compressor.initMechanicalLosses(120.0);

// Get results
double sealGas = compressor.getSealGasConsumption();  // Nm³/hr total
double bearingLoss = compressor.getBearingLoss();     // kW
double mechEfficiency = compressor.getMechanicalEfficiency();  // 0-1

System.out.println("Seal gas consumption: " + sealGas + " Nm³/hr");
System.out.println("Bearing power loss: " + bearingLoss + " kW");
System.out.println("Mechanical efficiency: " + (mechEfficiency * 100) + "%");

Seal Types

CompressorMechanicalLosses losses = compressor.getMechanicalLosses();

// Available seal types
losses.setSealType(CompressorMechanicalLosses.SealType.DRY_GAS_TANDEM);  // Most common
losses.setSealType(CompressorMechanicalLosses.SealType.DRY_GAS_DOUBLE);  // Lower leakage
losses.setSealType(CompressorMechanicalLosses.SealType.DRY_GAS_SINGLE);  // Higher leakage
losses.setSealType(CompressorMechanicalLosses.SealType.LABYRINTH);       // Non-contacting
losses.setSealType(CompressorMechanicalLosses.SealType.OIL_FILM);        // Legacy

Seal Gas Flows (API 692)

Flow Type Description Typical Range
Primary Leakage Gas escaping past primary seal 0.5-5 Nm³/hr per seal
Secondary Leakage Gas past secondary seal (tandem) 10-30% of primary
Buffer Gas Clean gas between seals 2-10 Nm³/hr per seal
Separation Gas N₂ to prevent oil mist ingress 1-5 Nm³/hr per seal 
// Individual seal gas flows
double primaryLeak = losses.calculatePrimarySealLeakage();    // Nm³/hr
double secondaryLeak = losses.calculateSecondarySealLeakage(); // Nm³/hr  
double bufferGas = losses.calculateBufferGasFlow();           // Nm³/hr
double separationGas = losses.calculateSeparationGasFlow();   // Nm³/hr

// Total consumption
double total = losses.getTotalSealGasConsumption();  // Nm³/hr

Bearing Types

// Available bearing types
losses.setBearingType(CompressorMechanicalLosses.BearingType.TILTING_PAD);    // Standard
losses.setBearingType(CompressorMechanicalLosses.BearingType.PLAIN_SLEEVE);   // Higher loss
losses.setBearingType(CompressorMechanicalLosses.BearingType.MAGNETIC_ACTIVE); // Very low loss
losses.setBearingType(CompressorMechanicalLosses.BearingType.GAS_FOIL);       // Oil-free

Bearing and Lube Oil Calculations (API 617)

// Bearing losses
double radialLoss = losses.calculateRadialBearingLoss();  // kW
double thrustLoss = losses.calculateThrustBearingLoss();  // kW
double totalBearingLoss = losses.getTotalBearingLoss();   // kW

// Lube oil system
losses.setLubeOilInletTemp(40.0);   // °C
losses.setLubeOilOutletTemp(55.0);  // °C

double oilFlow = losses.calculateLubeOilFlowRate();       // L/min
double coolerDuty = losses.calculateLubeOilCoolerDuty();  // kW

Configuration Options

CompressorMechanicalLosses losses = compressor.initMechanicalLosses(100.0);

// Seal configuration
losses.setSealType(CompressorMechanicalLosses.SealType.DRY_GAS_TANDEM);
losses.setNumberOfSeals(2);  // Typically 2 for single-shaft
losses.setSealGasSupplyPressure(105.0);  // bara
losses.setSealGasSupplyTemperature(40.0);  // °C

// Bearing configuration  
losses.setBearingType(CompressorMechanicalLosses.BearingType.TILTING_PAD);
losses.setNumberOfRadialBearings(2);

// Compressor updates operating conditions automatically
compressor.updateMechanicalLosses();

Complete Example

// Natural gas compressor with mechanical losses
SystemInterface gas = new SystemSrkEos(298.0, 50.0);
gas.addComponent("methane", 0.9);
gas.addComponent("ethane", 0.1);
gas.setMixingRule("classic");

Stream inlet = new Stream("inlet", gas);
inlet.setFlowRate(5000.0, "kg/hr");
inlet.run();

// Create and configure compressor
Compressor comp = new Compressor("HP Compressor", inlet);
comp.setOutletPressure(150.0, "bara");
comp.setPolytropicEfficiency(0.78);
comp.setSpeed(12000);
comp.run();

// Configure mechanical losses
CompressorMechanicalLosses losses = comp.initMechanicalLosses(120.0);
losses.setSealType(CompressorMechanicalLosses.SealType.DRY_GAS_TANDEM);
losses.setBearingType(CompressorMechanicalLosses.BearingType.TILTING_PAD);

// Print summary
System.out.println("=== Compressor Results ===");
System.out.println("Power: " + comp.getPower("kW") + " kW");
System.out.println("Polytropic head: " + comp.getPolytropicHead("kJ/kg") + " kJ/kg");
System.out.println();
System.out.println("=== Mechanical Losses ===");
System.out.println("Seal gas consumption: " + comp.getSealGasConsumption() + " Nm³/hr");
System.out.println("  - Primary leakage: " + losses.calculatePrimarySealLeakage() + " Nm³/hr");
System.out.println("  - Buffer gas: " + losses.calculateBufferGasFlow() + " Nm³/hr");
System.out.println("Bearing loss: " + comp.getBearingLoss() + " kW");
System.out.println("Mechanical efficiency: " + (comp.getMechanicalEfficiency() * 100) + "%");
System.out.println();
System.out.println("=== Lube Oil System ===");
System.out.println("Oil flow: " + losses.calculateLubeOilFlowRate() + " L/min");
System.out.println("Cooler duty: " + losses.calculateLubeOilCoolerDuty() + " kW");

Python Example

from jpype import JImplements, JOverride
from neqsim.thermo import fluid
from neqsim.process import compressor, stream

# Create gas and stream
gas = fluid('srk')
gas.addComponent('methane', 0.9)
gas.addComponent('ethane', 0.1)
gas.setMixingRule('classic')

inlet = stream(gas)
inlet.setFlowRate(5000.0, 'kg/hr')
inlet.setTemperature(25.0, 'C')
inlet.setPressure(50.0, 'bara')
inlet.run()

# Create compressor
comp = compressor(inlet)
comp.setOutletPressure(150.0)
comp.setPolytropicEfficiency(0.78)
comp.setSpeed(12000)
comp.run()

# Initialize mechanical losses (120mm shaft)
losses = comp.initMechanicalLosses(120.0)
losses.setSealType(losses.SealType.DRY_GAS_TANDEM)

# Get results
print(f"Seal gas consumption: {comp.getSealGasConsumption():.2f} Nm³/hr")
print(f"Bearing power loss: {comp.getBearingLoss():.2f} kW")
print(f"Mechanical efficiency: {comp.getMechanicalEfficiency()*100:.1f}%")