# Emission Spectroscopy-Based Sensor System to Correlate the In-Cylinder Combustion Temperature of a Diesel Engine to NOx Emissions

## TL;DR

This paper presents a sensor system using emission spectroscopy to measure in-cylinder combustion temperatures in a diesel engine and correlate them with NOx emissions.

## Contribution

A novel minimal invasive emission spectroscopy method is introduced to correlate in-cylinder temperature with NOx emissions in diesel engines.

## Key findings

- The in-cylinder temperature measurements showed a strong correlation with exhaust NOx concentrations.
- A standard deviation of 25 K to 49 K was observed in the in-cylinder temperature measurements.
- The method uses soot as a black body radiator and Planck’s law for spectral evaluation.

## Abstract

Due to a rising importance of the reduction of pollutant, produced by conventional energy technologies, the knowledge of pollutant forming processes during a combustion is of great interest. In this study the in-cylinder temperature, of a near series diesel engine, is examined with a minimal invasive emission spectroscopy sensor. The soot, nearly a black body radiator, emits light, which is spectrally detected and evaluated with a modified function of Planck’s law. The results show a good correlation between the determined temperatures and the NOx concentration, measured in the exhaust gas of the engine, during a variety of engine operating points. A standard deviation between 25 K and 49 K was obtained for the in-cylinder temperature measurements.