It is noticed that one of the most difficult measurement for IC engine is to measure correct exhaust manifold pressure.
The model GCM200 is an only pressure gauge in the world to be able to measure the exhaust manifold pressure correctly under very high temperature up to 800C, pressure pulsating violently from -80 to 500kPa, strong vibration from 20 to 50G and the fast response from DC to 5kHz are also desired.
It may be destroyed for lack of cooling water if the water cooled type pressure transducer with strain gauges is used and this may lead to the large drift of sensitivity and will cause a problem. It is not able to use this in high accuracy due to less S/N ratio caused by the vibration from exhaust system.
The temperature drift is reduced by using a water cooled Piezo-electric transducer but no absolute pressure signal is provided and this may lead to a big problem to determine the atmospheric base line for measuring catalyst gas flow, pressure drop across DPF and the gas exchange rate in DPF.
The model GCM200 is an only reliable pressure gauge to be able to measure the exhaust pressure accurately with fast response and high S/N ratio by employing the water cooled Piezo-electric transducer.
The unique system of GCM200 to separate the pressure dynamic range in low frequency and in high frequency respectively enable to measure the exhaust manifold pressure accurately with fast response and high S/N ratio.
- Essentially low drift up to the ambient temperature in 800C.
- Excellent response time from DC to 5 kHz and measure the exhaust manifold pressure accurately over 720CA and it can also detect the correct atmospheric base line with this DC characteristic to research and develop catalysts and DPFs.
- Detect the vacuum pressure in exhaust manifold accurately due to configuring the compound pressure gaugeeously.
- Practical results with harsh motor sports engine prove the reliability of GCM200.
|Measurement mode||Compound pressure|
|Pressure range||-80 - 100kPa (available 300kPafor diesel engine)|
|Ambient temperature||5 - 800C (compulsory water cooled Piezo-electric transducer)|
|Response time||DC - 5kHz +/-0.5dB|
|Analogue output||-80 - 0 - 100kPa : -8 - 10V|
- Accurate exhaust manifold pressure measurement based on the atmospheric base pressure line for catalysts and DPFs research.
- Accurate analysis of gas exchange process combined with dynamic pressure measurement.
- Accurate pressure measurement for exhaust system developing simulation
Pressure gauge PEN-33
One of the most difficult applications to measure the pressure for IC engine is a dynamic exhaust manifold pulsating pressure measurement with fast response under high temperature conditions. The static exhaust manifold pressure measurement is performed by introducing the pressure away from an exhaust manifold under almost ambient temperature.
The engine research for modern HCCI engine based on the Lean or Stratified Combustion is required to measure the fluctuated pressure with fast response within one engine cycle.
The dynamic pressure measurement in the exhaust manifold is normally performed under the following conditions:
-1. Exhaust temperature : > 800C
-2. Pressure : Pulsation pressure from -80 to 500 kPa
-3. Vibration : 20 to 50G
-4. Frequency response : DC to 5 kHz
The typical pressure transducer applicable for the exhaust manifold pulsating pressure with high temperature is normally the Piezo-Electric one and the GaPO4 transducer is applied up to 400C without cooling. But the water cooled Pezo-electric type is the only pressure transducer to be able to apply to the temperature up to 800C under high engine load or high engine speed conditions.
High sensitivity due to relatively low pressure is required to measure the exhaust manifold pressure and the pressure is affected by the resonance between cylinders.
The long pressure leads away from exhaust manifold to decrease the temperature to the pressure transducer increase dead volume and leads to loose the response time significantly worse and causes the error due to the pulsation pressure phase problem.
The water cooled Piezo-electric pressure transducers with 14mm thread size or water cooled pressure transducers with strain gages were used so far for these applications. But both types of pressure transducer have some weak points as the former one can not provide absolute pressure by the lack of DC signals due to an increase of cut-off frequency, however the latter one can provide absolute pressure but shows significant temperature drift and decrease the S/N ratio with low sensitivity.
Sokken have succeeded to modify an exhaust manifold pressure gauge for the practical use by compensating the frequency response in low frequency ranges with strain gauges and long pressure leads based on a standard water cooled Piezo-electric transducer (8 to 14mm) with high frequency response and Sokken acquired the patent(No. 3523206) in Japan.
The details of the exhaust manifold pressure gage for the model GCM200 is described in below:
The system diagram is shown in the above diagram and the pressure taps are shown in the drawing below.
It is required to detect the exhaust manifold pressures simultaneously for both averaging and pulsating pressures respectively. The dynamic pressure measurement from a few hertz to some megahertz is assigned to a pulsating pressure measurement block and the static pressure measurement from DC to a few hertz is assigned to an averaging pressure measurement block. The frequency response is very important for both pressure taps and pressure leads. The pulsating and averaging pressures crosses over at a few hertz point so that it is required to flatten the response time of pressure leads for the averaging pressure in order to prevent the effects of amplitude and phase angle at the crossed over point. A low-pass filter allows passing the averaging pressure signals less than a few hertz and a high-pass filter allows passing the pulsating pressure signals greater than 1.6 hertz. The model GCM200 provides a flat pressure output over DC to 5 kHz by adding these signals.
The specimen data of an absolute exhaust manifold pressure trace from the model GCM200 is shown in the graph below.
It is clearly observed a varied exhaust manifold pressure within one engine cycle together with the in-cylinder pressure and absolute intake manifold pressure. The engine condition for this test is low load and low speed.