Calculate the percentage of Exhaust Gas Recirculation based on mass flow rates.
Use consistent units (e.g., g/s, kg/h, lb/min)
Must use the same unit as Fresh Air
Calculated EGR Rate0.00%
Total Mass Flow (Charge)0
Fresh Air Fraction0.00%
function calculateEGR() {
// Get input elements by ID
var freshAirInput = document.getElementById('freshAirFlow');
var egrGasInput = document.getElementById('egrGasFlow');
// Parse values
var mAir = parseFloat(freshAirInput.value);
var mEGR = parseFloat(egrGasInput.value);
// Validation logic
if (isNaN(mAir) || isNaN(mEGR)) {
alert("Please enter valid numeric values for both flow rates.");
return;
}
if (mAir < 0 || mEGR < 0) {
alert("Flow rates cannot be negative.");
return;
}
// Calculate Total Mass Flow
var totalFlow = mAir + mEGR;
// Prevent division by zero
if (totalFlow === 0) {
alert("Total flow cannot be zero. Please check your inputs.");
return;
}
// Calculate EGR Rate Formula: (mEGR / (mAir + mEGR)) * 100
var egrRate = (mEGR / totalFlow) * 100;
// Calculate Fresh Air Fraction for context
var airFraction = (mAir / totalFlow) * 100;
// Display Results
document.getElementById('finalEgrRate').innerHTML = egrRate.toFixed(2) + '%';
document.getElementById('totalFlowResult').innerHTML = totalFlow.toFixed(2) + ' (units)';
document.getElementById('airFractionResult').innerHTML = airFraction.toFixed(2) + '%';
// Show result container
document.getElementById('resultContainer').style.display = 'block';
}
function resetCalculator() {
document.getElementById('egrForm').reset();
document.getElementById('resultContainer').style.display = 'none';
}
Understanding EGR Rate Calculation
Exhaust Gas Recirculation (EGR) is a crucial emission control technology used in internal combustion engines (primarily diesel and modern gasoline engines) to reduce Nitrogen Oxides (NOx). The EGR Rate defines the proportion of recirculated exhaust gas relative to the total gas mixture entering the engine cylinders.
The EGR Rate Formula
The standard engineering method for determining the EGR rate is based on mass flow. The formula calculates the ratio of the mass of the recirculated gas to the total mass of the intake charge (fresh air plus recirculated gas).
EGR Rate (%) = [ Megr / ( Mair + Megr ) ] × 100
Where:
Megr: The mass flow rate of the recirculated exhaust gas.
Mair: The mass flow rate of the fresh intake air (usually measured by the MAF sensor).
Why Calculate EGR Rate?
Accurate calculation of the EGR rate is vital for automotive engineers and tuners for several reasons:
NOx Reduction: EGR lowers the peak combustion temperature. Since NOx formation is highly temperature-dependent, a specific EGR rate helps keep combustion temperatures below the threshold where NOx forms rapidly.
Engine Efficiency: While EGR reduces emissions, excessive EGR can lead to incomplete combustion, increased particulate matter (soot), and reduced power. Calculating the optimal rate balances emissions against performance.
Diagnostics: By comparing expected EGR rates (commanded by the ECU) with calculated rates (derived from sensor data like MAF and O2 sensors), mechanics can diagnose clogged EGR valves or cooler leaks.
Example Calculation
Suppose an engine operating at a steady cruise has the following parameters measured by its sensors:
Fresh Air Flow (MAF): 200 g/s
EGR Flow Estimate: 50 g/s
Using the calculator above:
Total Flow = 200 + 50 = 250 g/s
EGR Rate = (50 / 250) × 100 = 20%
This means 20% of the gas entering the cylinder is inert exhaust gas, which will help suppress NOx formation during combustion.
Important Considerations
Units: While the calculator works with any unit, ensure that both Mair and Megr are in the same unit (e.g., both in grams per second or kilograms per hour) before calculating.
Gas Density: This calculator assumes mass flow rates. If you only have volumetric flow rates (e.g., CFM), you must correct for density differences between the cool fresh air and the hot EGR gas to get accurate results.