Refine Your Search

Search Results

Viewing 1 to 3 of 3
Technical Paper

Non-Invasive Differential Thermocouple Method for the Evaluation of Catalyst Performance

A simple non-invasive thermocouple method is described and demonstrated that provides catalyst performance information. The thermocouple circuit consists of a Chromel wire attached to the stainless steel exhaust system before the catalyst and another Chromel wire after the catalyst. The exhaust system stainless steel functions as the other dissimilar metal component of a differential thermocouple. Measured electromotive force (EMF) between the thermocouple leads is proportional to the temperature difference across the catalyst and allows assessment of the performance of the catalyst between the thermocouple junctions. By measuring the difference directly, rather than measuring at two locations and using the difference between high temperatures at the two locations, one obtains a relatively accurate measurement even without calibration. A series of experiments were carried out to demonstrate the catalyst monitoring capabilities of this methodology.
Technical Paper

Estimating Actual Exhaust Gas Temperature from Raw Thermocouple Measurements Acquired During Transient and Steady State Engine Dynamometer Tests

Thermocouples are commonly used to measure exhaust gas temperature during automotive engineering experiments. In most cases, the raw measurements are used directly as an absolute indication of the actual exhaust gas temperature. However, in reality, the signal from a TC is only an indication of its own tip temperature. The TC indicated tip temperature can deviate significantly from the actual gas temperature due to factors such as thermal capacitance of the tip itself, and heat transfer to the exhaust pipe wall through conduction and radiation. A model has been developed that calculates the effects of these factors to provide an estimate of the actual exhaust gas temperature. Experiments were performed to validate the model under both transient and steady state engine dynamometer conditions utilizing three popular sizes of TCs. Good correlation among predictions for various TC sizes confirms the model's accuracy.
Technical Paper

A Simplified Method to Make Temperature Measurements of a Metal Surface using the Surface as One Component of Thermocouple

Instrumentation of an exhaust system to measure surface temperature at multiple locations usually involves welding independent thermocouples to the surface of the system. This report describes a new type of thermocouple fabricated to measure temperature at a point or temperature difference between points on a metallic object utilizing the metal as one component of the new thermocouple. AISI 316 stainless steel is used in the current study to represent automotive exhaust pipe. The other component of the thermocouple is Nickel-Chromium (Chromel, Chromega), one of the two metals used in type K thermocouples, which are generally used for exhaust temperature measurements during emission tests. Use of the new thermocouple is contingent upon an accurate calibration of its response to changes in temperature.