First Unsteady Pressure Measurements With a Fast Response Cooled Total Pressure Probe in High Temperature Gas Turbine Environments

Abstract

This paper presents the first experimental engine and test rig results obtained from a fast response cooled total pressure probe. The first objective of the probe design was to favor continuous immersion of the probe into the engine to obtain time series of pressure with a high bandwidth and therefore statistically representative average fluctuations at the blade passing frequency. The probe is water cooled by a high pressure cooling system and uses a conventional piezo-resistive pressure sensor which yields therefore both time-averaged and time-resolved pressures. The initial design target was to gain the capability of performing measurements at the temperature conditions typically found at high pressure turbine exit (1100–1400K) with a bandwidth of at least 40kHz and in the long term at combustor exit (2000K or higher). The probe was first traversed at the turbine exit of a Rolls-Royce Viper turbojet engine, at exhaust temperatures around 750 °C and absolute pressure of 2.1bars. The probe was able to resolve the high blade passing frequency (≈23kHz) and several harmonics up to 100kHz. Besides the average total pressure distributions from the radial traverses, phase-locked averages and random unsteadiness are presented. The probe was also used in a virtual three-hole mode yielding unsteady yaw angle, static pressure and Mach number. The same probe was used for measurements in a Rolls-Royce intermediate pressure burner rig. Traverses were performed inside the flame tube of a kerosene burner at temperatures above 1600 °C. The probe successfully measured the total pressure distribution in the flame tube and typical frequencies of combustion instabilities were identified during rumble conditions. The cooling performance of the probe is compared to estimations at the design stage and found to be in good agreement. The frequency response of the probe is compared to cold shock tube results and a significant increase in the natural frequency of the line-cavity system formed by the conduction cooled screen in front of the miniature pressure sensor were observed.

High-temperature high-frequency turbine exit flow field measurements in a military engine with a cooled unsteady total pressure probe

“…The fundamental BPV is 17.05 kHz, and five harmonics, (1) to (5), are clearly seen. The resonance around 137 kHz, (6), is the line-cavity resonance frequency at the flow temperature. It shall be noted that this frequency, found to be around 35 kHz at room temperature, is increasing with cavity gas temperature as presented before by the authors [6].…”

“…In this article, a short summary of literature will be presented as the full literature review has been presented by the authors in references [4], [5], and [6].…”

“…Unsteady pressure measurements on a more general level have been the topic of various interesting review papers in which more information can be found. In this article, a short summary of literature will be presented as the full literature review has been presented by the authors in references [4], [5], and [6].…”

“…Following hydraulic verifications, a first prototype was assembled and sealed while protecting electrical solders from the coolant using resin. After the testing of the first prototype on several test vehicles [5,6], the electrical splicing layout has been altered, hermetically sealing the sensor wires from the coolant. Another change for the second prototype was the use of a leadless sensor, where the sensor chip is brazed to the wires instead of a wire bonding process.…”

Turbulent velocity and pressure fluctuations in gas turbine combustor exit flows

“…Brouckaert et al 31 and Mersinligil et al 32,33 developed water-cooled pressure probes using ultraminiature Kulite piezoresistive transducers. Whilst such probes were not used to measure turbulence, they could conceivably be calibrated to do so.…”